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12-01-2012, 01:00 PM
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#1
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Newbie
Join Date: Oct 2010
Posts: 18
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Grounding With Metal Boxes
How do you guys do your ground? I've seen this a few times with metal boxes. They say you can ground on the wire nuts like that and then when the metal outlet tabs and screws are screwed into the metal box that it grounds itself without using the ground screw on the outlet and in the box. What are the pros/cons of this?
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12-01-2012, 01:04 PM
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#2
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Newbie
Join Date: Dec 2012
Posts: 2
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Grounding With Metal Boxes
In side the box is a grounding screw, that is where it should be grounded both to the box and the device. The way it is now if by some chance the ground becomes hot it could melt the casing and start a toxic fire in the wall.
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12-01-2012, 01:04 PM
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#3
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Member
Join Date: Oct 2012
Location: Bluefield, VA (SW VA)
Posts: 41
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Grounding With Metal Boxes
Doesn't seem like the most secure connection for a ground. Should make a pigtail from the box, pigtail to outlet ground screw, and connect those to incoming ground(s)
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12-01-2012, 01:11 PM
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#4
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Newbie
Join Date: Oct 2010
Posts: 18
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Grounding With Metal Boxes
Quote:
Originally Posted by padraic
In side the box is a grounding screw, that is where it should be grounded both to the box and the device. The way it is now if by some chance the ground becomes hot it could melt the casing and start a toxic fire in the wall.
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Wouldn't it melt and cause a fire either way if the ground became hot?
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12-01-2012, 01:12 PM
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#5
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E2 Electrician
Join Date: Apr 2012
Location: Litchfield, CT
Posts: 3,069
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Grounding With Metal Boxes
Quote:
Originally Posted by cre10
Wouldn't it melt and cause a fire either way if the ground became hot?
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it won't melt.... the job of the grounding conductor is to clear a fault, in order to do this, it MUST become energized...
Why people throw out comments at will is beyond me.
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12-01-2012, 01:15 PM
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#6
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Newbie
Join Date: Oct 2010
Posts: 18
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Grounding With Metal Boxes
Quote:
Originally Posted by stickboy1375
it won't melt.... the job of the grounding conductor is to clear a fault, in order to do this, it MUST become energized...
Why people throw out comments at will is beyond me.
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So how wrong/dangerous is the picture?
It seems to be ok as long as you don't remove the outlets because then the ground would be gone?
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12-01-2012, 01:15 PM
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#7
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E2 Electrician
Join Date: Apr 2012
Location: Litchfield, CT
Posts: 3,069
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Grounding With Metal Boxes
The grounding install is all wrong, for whatever reason, that technique was used early on, but the grounding conductor must be made up inside the box, the metal box and device all bonded together.
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12-01-2012, 01:16 PM
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#8
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E2 Electrician
Join Date: Apr 2012
Location: Litchfield, CT
Posts: 3,069
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Grounding With Metal Boxes
Quote:
Originally Posted by cre10
So how wrong/dangerous is the picture?
It seems to be ok as long as you don't remove the outlets because then the ground would be gone?
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its far from okay, fix the issue.
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12-01-2012, 01:17 PM
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#9
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Newbie
Join Date: Oct 2010
Posts: 18
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Grounding With Metal Boxes
Quote:
Originally Posted by stickboy1375
The grounding install is all wrong, for whatever reason, that technique was used early on, but the grounding conductor must be made up inside the box, the metal box and device all bonded together.
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How long ago was that technique used?
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12-01-2012, 01:18 PM
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#10
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E2 Electrician
Join Date: Apr 2012
Location: Litchfield, CT
Posts: 3,069
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Grounding With Metal Boxes
Quote:
Originally Posted by cre10
How long ago was that technique used?
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A long time ago back when NM had a cloth jacket and it was done much nicer than in your picture, thats a new install, but some hack did the work.
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12-01-2012, 01:20 PM
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#11
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Licensed electrician
Join Date: Sep 2007
Location: Maryland
Posts: 5,942
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Grounding With Metal Boxes
Probably 40 years ago or more.
The sheath must extend into the box at least 1/4". All grounds need to be connected together and to the box and device.
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Answers based on the National Electrical Code. Local amendments may apply. Check with your local building officials.
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12-01-2012, 02:13 PM
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#12
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Member
Join Date: Oct 2009
Posts: 452
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Grounding With Metal Boxes
Quote:
Originally Posted by cre10
So how wrong/dangerous is the picture?
It seems to be ok as long as you don't remove the outlets because then the ground would be gone?
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It is an incredibly sloppy application, there is no way that it is OK.
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12-01-2012, 03:21 PM
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#13
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Civil Engineer
Join Date: Mar 2009
Location: Boston
Posts: 3,553
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Grounding With Metal Boxes
Yes it is sloppy, but let's back up for a second. My entire house was grounded in a similar manner. House was built in 1959, I a guessing that the technique of wrapping wire around a screw on the outside of a metal box was pretty typical in 1959. And the technique likely violates current NEC requirements, since the grounding wire is apparently supposed to be connected to a green grounding screw inside the box. But the technique certainly works electrically, since the copper grounding wire is mechanically connected to the box.
Assuming the outlet grounding wire is connected to a grounding screw inside the box via a pigtail, the system is electrically grounded. I would class this as a technical violation of NEC, and if the wire was installed some years ago, it may have been compliant with regulations at the time, in which case it may be grandfathered. Is it worth fixing? Probably, but does not look like a really high priority. If the outlet is ungrounded, that is a more serious problem, but you can't tell from the photo.
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12-01-2012, 03:25 PM
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#14
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E2 Electrician
Join Date: Apr 2012
Location: Litchfield, CT
Posts: 3,069
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Grounding With Metal Boxes
Quote:
Originally Posted by Daniel Holzman
Yes it is sloppy, but let's back up for a second. My entire house was grounded in a similar manner. House was built in 1959, I a guessing that the technique of wrapping wire around a screw on the outside of a metal box was pretty typical in 1959. And the technique likely violates current NEC requirements, since the grounding wire is apparently supposed to be connected to a green grounding screw inside the box. But the technique certainly works electrically, since the copper grounding wire is mechanically connected to the box.
Assuming the outlet grounding wire is connected to a grounding screw inside the box via a pigtail, the system is electrically grounded. I would class this as a technical violation of NEC, and if the wire was installed some years ago, it may have been compliant with regulations at the time, in which case it may be grandfathered. Is it worth fixing? Probably, but does not look like a really high priority. If the outlet is ungrounded, that is a more serious problem, but you can't tell from the photo.
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It's a hacked installation, and the yellow NM shows it's not an old installation. And ground screw does not have to be green.
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12-01-2012, 03:32 PM
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#15
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A "Handy Husband"
Join Date: Feb 2007
Location: South Carolina Low Country
Posts: 2,930
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Grounding With Metal Boxes
Quote:
Originally Posted by stickboy1375
A long time ago back when NM had a cloth jacket and it was done much nicer than in your picture, thats a new install, but some hack did the work.
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It was done back in the 50's through the 60's (when grounded cables became a requirement), primarily in the Northeast. And hence the name "Boston Back wrap". But even then the sheathe was brought into the box and the ground was wrapped tightly back around the cable and secured under the clamp. Even if done correctly it is no longer compliant.
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